Downhole completion system with retrievable power unit

ABSTRACT

A technique facilitates providing a downhole completion with electrical power. The technique may comprise placing an independent completion in a wellbore section. The independent completion is provided with a removable power unit having a power generator coupled to a power storage device. The technique further comprises communicating data or other signals between the independent completion located in the wellbore section and a second completion located in a separate wellbore section.

CROSS-REFERENCE TO RELATED APPLICATION

The present document is based on and claims priority to U.S. ProvisionalApplication Ser. No.: 61/385,229, filed Sep. 22, 2010, incorporatedherein by reference.

BACKGROUND

Hydrocarbon fluids, e.g. oil and natural gas, are obtained from asubterranean geologic formation, referred to as a reservoir, by drillinga well that penetrates the hydrocarbon-bearing formation. Once awellbore is drilled, various forms of well completion components may beinstalled to control and enhance the efficiency of producing fluids fromthe reservoir. However, many downhole components, e.g. sensors andelectrically actuated valves, require power to function properly.

To provide power downhole, attempts have been made to utilize downholepower generation devices. For example, permanent magnet generators havebeen combined with turbines and located downhole in a wellbore. However,if constant power generation is required from the generator, thewellbore section containing the power generation device must remain opento provide continuous flow through the turbine. In some applications,the downhole power generation devices have been used to generate powerfor driving a hydraulic pump which, in turn, hydraulically actuates flowcontrol valves. However, such systems have limited use for poweringdownhole electrical components. Additionally, retrieval and servicing ofexisting power generation devices tends to be a complex andtime-consuming process.

SUMMARY

In general, the present disclosure provides a technique for supplying adownhole completion with electrical power. According to one embodiment,the technique comprises placing an independent completion in a wellboresection. The independent completion is provided with a removable powerunit having a hydraulically driven power generator coupled to a powerstorage device. The technique further comprises communicating data orother signals between the independent completion located in the wellboresection and a second completion located in a separate wellbore section.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the disclosure will hereafter be described withreference to the accompanying drawings, wherein like reference numeralsdenote like elements, and:

FIG. 1 is a schematic illustration of a well system deployed in awellbore and including an independent completion with a removable powerunit positioned in a wellbore section and another completion deployed ina different wellbore section, according to an embodiment of the presentdisclosure;

FIG. 2 is a schematic illustration similar to the illustration in FIG. 1but showing a plurality of independent completions deployed in lateralwellbores and communicating with a completion deployed in a primary orvertical wellbore section, according to an embodiment of the presentdisclosure; and

FIG. 3 is an illustration of an example of an independent completioncomprising a power unit with a power generator and a power storagedevice deployed in a wellbore, according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of the present disclosure. However, it will beunderstood by those of ordinary skill in the art that the presentdisclosure may be practiced without these details and that numerousvariations or modifications from the described embodiments may bepossible.

The disclosure herein generally relates to a system and methodologyregarding well completion systems and more particularly to wellcompletion systems having a retrievable downhole power generating unit.According to one embodiment, an independent completion is deployed in awellbore section, such as a lateral wellbore section or other desiredwellbore section. The independent completion comprises a removable powerunit having a power generator and a power storage coupled to the powergenerator. The well system also may comprise a telemetry system forcommunicating data between the independent completion and anothercompletion located in a different wellbore section. By way of example,the telemetry system may comprise a wireless telemetry system, such asan electromagnetic wireless telemetry system or a pressure pulsetelemetry system.

In some embodiments, the independent completion comprises a turbinepower generator which provides power for monitoring and controlling wellfluid production within a wellbore section. The independent completionmay be a fully self-sustained system so that no hard wire is requiredbetween the wellbore section, e.g. a lateral wellbore section, and asecond completion located in a second wellbore section, e.g. in amotherbore. Communication signals may be passed between the independentcompletion and the second completion via the wireless telemetry system.Additionally, the communication signals may be relayed between thesecond completion and a control system located at the surface.

Power generated by the turbine power generator within the wellboresection may be stored in a suitable power storage device. By way ofexample, the power storage device may comprise one or more batteries,e.g. rechargeable batteries, which directly power electrical devices inthe independent completion. For example, the electrical power may beused to power electric flow control valves and/or sensors located withinthe wellbore section. As the batteries become depleted, furtherproduction fluid spins the turbine of the turbine power generator togenerate power for recharging batteries, thus increasing the life of thedownhole independent completion system. Additionally, the entire powerunit comprising the power generator and the power storage device may beremovable and retrievable to the surface. The power unit may be coupledto the remainder of the independent completion by a suitable coupling,such as an inductive coupling, to enable retrieval and servicing of thepower unit. After servicing, the power unit can be re-deployed andreengaged with the remainder of the independent completion in thewellbore section (e.g. a lateral wellbore section or a portion of avertical wellbore) for extended use during another service lifetime.

In some embodiments, the independent completion comprises an intelligentcompletion system which may be deployed in the downhole lateral wellboresection and used to power, for example, electric flow control valves.Within the lateral wellbore section, the independent completion maycomprise numerous flow control valves which are used in cooperation withone or more production packers to isolate a plurality of production wellzones. The multiple electric flow control valves can be controlled viaelectric power provided by the power unit of the independent completion.The ability to intelligently control each production well zone along thelateral wellbore section can substantially enhance hydrocarbon recovery.In some applications, the wireless telemetry system is used to eliminatethe challenges associated with routing a cable through a lateral windowand with forming cable connections downhole. In other applications,however, the independent completion may be used in a non-lateral, e.g. avertical, wellbore. For example, downhole power generation can be usedfor re-completing vertical wells which have no existing electrical feedthrough the wellhead. Downhole power generation combined with a wirelesstelemetry system enables monitoring and control without incurring thecost and inconvenience of replacing the wellhead and tubing hanger.

Referring generally to FIG. 1, an embodiment of a well system 20 isillustrated as deployed in a well 22 having a wellbore section 24 and atleast one additional wellbore section 26, such as a generally verticalwellbore section. Depending on the application, wellbore section 24 maybe a lateral wellbore section or a vertical wellbore section. In theexample illustrated, the wellbore section 26 is a generally verticalwellbore section which may comprise a motherbore from which one or morelateral wellbore sections 24 extend. In this embodiment, a wellcompletion 28 is deployed in the wellbore section 26, and an independentcompletion 30 is deployed in the wellbore section 24, e.g. in a lateralwellbore section. In at least some applications, the independentcompletion 30 is a fully self-sustained system with no hard wireconnection to the well completion 28.

The well completion 28 may comprise a variety of components and systems32 to facilitate, for example, production and/or injection of fluids.One or more packers 34 may be employed to segregate well zones 36 alongwellbore section 26. Similarly, independent completion 30 may comprise avariety of components and systems to facilitate the flow of productionfluid and/or injection fluids with respect to one or more well zones 38located along lateral wellbore section 24.

In the embodiment illustrated, independent completion 30 comprises atleast one tubing or housing section 40 and one or more packers 42surrounding tubing section 40 to isolate the desired well zone(s) 38along lateral wellbore section 24. The independent completion 30 alsocomprises a power unit 44 which is removably engaged with the remainderof independent completion 30, e.g. with tubing section 40. By way ofexample, the power unit 40 comprises a power generator 46 and a powerstorage device 48 operatively coupled with the power generator 46. Byway of further example, the power generator 46 may be a hydraulicallydriven generator, such as a turbine generator, which is rotated by fluidflow along independent completion 30. For example, the flow ofproduction fluid into lateral wellbore 24 from one or more well zones 38of the surrounding formation 50 may be used to drive the turbine orother type of hydraulically driven power generator 46.

The resulting electrical power can be used to charge power storagedevice 48 and/or to directly power a variety of electrical devices 52positioned in independent completion 30 or at other locations along thelateral wellbore section 24 or at other suitable downhole locations. Thepower storage device 48 may be in the form of a battery, e.g. arechargeable battery, which can be charged by the power/current outputfrom power generator 46. This allows the power storage device 48 toprovide power for electrical devices 52 even when lateral wellboresection 24 is shut-in or during other periods when no fluid flowsthrough power generator 46.

Electrical devices 52 may comprise a wide variety of electricallypowered devices, and the specific types of devices 52 depend on thedesign of independent completion 30 as well as on operational and/orenvironmental considerations. The power unit 44 may be used to providepower for a single electrical device 52 or for multiple electricaldevices 52. By way of example, electrical devices 52 may comprise one ormore flow control valves 54 and one or more sensors 56. The electricflow control valves 54 and the sensors 56 may be placed in the wellzones 38 along lateral wellbore section 24. Power may be provided toelectrical devices 52 and/or data signals may be output from sensors 56or other electrical devices 52 through suitable conductors 58. Becausethe power unit 44 may be selectively engaged and disengaged from theremainder of independent completion 30, a suitable coupling mechanism 60is employed to enable selective engagement of the power unit 44 whilealso enabling transfer of signals to or from conductors 58. By way ofexample, the coupling mechanism 60 may comprise an inductive coupler.

In some applications, no hard wired connections exist betweenindependent completion 30 and well completion 28. In these applications,signals are transferred via a wireless telemetry system 62. The wirelesstelemetry system 62 may be used to convey control signals from wellcompletion 28 to independent completion 30 and its electrical devices52. For example, signals may be transmitted downhole from a surfacecontrol system 64 to a first transceiver 66 of the wireless telemetrysystem 62 and those signals are transmitted wirelessly to a secondtransceiver 68 of wireless telemetry system 62 located on independentcompletion 30. Similarly, the wireless telemetry system 62 may be usedto transmit sensor data and other data wirelessly from independentcompletion 30 to well completion 28 for relay uphole to surface controlsystem 64. Although the independent completion 30 and wireless telemetrysystem 62 are amenable to use in lateral wellbores, the wellbore section24 also may be a vertical wellbore section capable of receivingindependent completion 30. In some applications, for example, downholepower generation may be employed in a vertical wellbore and wirelesscommunication can be established through a tubing hanger located below atree. This approach can be used in, for example, a re-completion inwhich the existing wellhead and tubing hanger do not have an electricalfeed through. The downhole power can be used even though there is noelectrical hardware through the existing surface or subsea wellheads.

Referring generally to FIG. 2, another embodiment of well system 20 isillustrated. In this embodiment, the wellbore section 26 is a generallyvertical wellbore from which a plurality of the lateral wellbores 24extend. In each of the illustrated lateral wellbore sections 24, anindependent completion 30 is deployed. The independent completions 30are each fully self-sustained systems which independently communicatewith well completion 28 in vertical wellbore 26 via wireless telemetrysystem 62. The overall system enables independent flow control and/orother control functions in each lateral wellbore section 24 withoutrequiring connecting equipment or electrical cables between theindependent completions 30 and the well completion 28.

In the embodiment illustrated in FIG. 2, each independent completion 30comprises removable and retrievable power unit 44. As similarlydescribed with reference to FIG. 1, each power unit 30 comprises thepower generator 46 coupled with the corresponding power storage device48. This enables electrical power to be supplied to electrical devices52, e.g. flow control valves 54 and sensors 56, via the power generator46 and/or the power storage device 48. The wireless telemetry system 62may be designed to independently handle transmission of data signalsfrom each of the independent completions 30 and to transmit controlsignals to specific independent completions 30 so as to control fluidflow and/or other functions within each lateral wellbore section 24.

In the embodiments illustrated in FIGS. 1 and 2, the power unit 44 maybe retrieved when necessary to recharge the power storage device 48, toservice the power unit 44, or to replace the power unit 44 with a new ordifferent power unit. For retrieval, the power unit 44 may be coupledwith an appropriate fishing tool or other retrieval tool and pulled to asurface location. For example, the power unit 44 may be sized forretrieval up through an interior of the well completion 28 located inwellbore section 26. The new or serviced power unit 44 is then simplyconveyed downhole through the interior of well completion 28 andre-engaged with the remainder of the corresponding independentcompletion 30 residing in the corresponding wellbore section 24, e.g. acorresponding lateral wellbore section or suitable non-lateral wellboresection.

Referring generally to FIG. 3, a more detailed example of overallwellbore system 20 and of independent completion 30 is illustrated.However, the independent completion 30, as well as other components andsystems of the overall well system 20, may be adjusted with a variety ofadditional and/or alternate components and systems. The specificcomponents and the arrangement of components and systems depends on theparameters of a given application and environment.

In the example illustrated, the power unit 44 comprises power generator46 in the form of a turbine generator 70 and further comprises powerstorage 48 in the form of a rechargeable battery 72. The power unit 44also includes coupling mechanism 60 in the form of an inductive coupler74. Turbine generator 70 and rechargeable battery 72 are electricallycoupled to electrical devices 52 via inductive coupler 74. For example,electrical power signals and/or data signals may be transferred throughinductive coupler 74 to or from electrical devices, such as electricalflow control valve 54, sensors 56, and a corresponding telemetry unit 76which is used to transfer signals to or from electric flow control valve54 and/or sensors 56 via conductors 58 in cooperation with inductivecoupler 74.

In the embodiment illustrated in FIG. 3, the power unit 44 may besecured within an expanded housing portion 78 via a locking mechanism 80disposed between power unit 44 and housing portion 78. The electricalflow control valve 54 is powered by power unit 44 and actuated toselectively control the flow of fluid, e.g. production fluid, alonglateral wellbore section 24. For example, the electrical flow controlvalve 54 may be selectively opened to enable flow of well fluid from thesurrounding well zone 38 into independent completion 30 throughappropriate inlet ports 82. The well fluid then flows through the flowcontrol valve 54 and along an interior of independent completion 30, asrepresented by arrows 84. The production fluid continues to flow throughan interior of the inductive coupler 74 and is released into expandedhousing portion 78, as represented by arrows 86.

Once in expanded housing portion 78, the production fluid flows along anexterior of rechargeable battery 72 within the expanded housing portion78 until passing through turbine generator 70. The flow of fluid throughturbine generator 70 causes rotation of the turbine and generation ofelectrical power which is supplied to rechargeable battery 72 and/or toelectrical devices 52 of independent completion 30 via conductors 58.After passing through turbine generator 70, the produced well fluidcontinues to flow into vertical wellbore section 26 and up through wellcompletion 28 for production to a desired surface location. In someembodiments, the well completion 28 may comprise one or more electricsubmersible pumping systems designed to produce fluid to the surfacelocation while drawing fluid into the lateral wellbore section 24.

The embodiment illustrated in FIG. 3 illustrates a single packer 42,however additional packers 42 may be used to isolate additional wellzones 38 along lateral wellbore section 24. Furthermore, a variety oftelemetry systems 62 may be employed to communicate signals between theindependent completion 30 and the well completion 28 located in adifferent wellbore section. As discussed above, the telemetry system maycomprise a wireless telemetry system, such as an acoustic telemetrysystem or an electromagnetic wireless telemetry system. In the specificexample illustrated, telemetry system 62 may comprise an electromagneticwireless telemetry system or an acoustic telemetry system.

The downhole turbine generator 70, battery 72, inductive coupler 74, andwireless telemetry system 62 may be used in cooperation to fully controland power the independent, intelligent completion 30 located in lateralwellbore section 24. As the turbine generator 70 is rotated by theflowing well fluid, electrical signals are output and those electricalpower signals may be rectified into a DC signal for charging the battery72. When a wireless command from the surface is transmitted to theindependent completion 30 via wireless telemetry system 62 to, forexample, open a valve or to transmit a sensor reading, the battery 72sends the correct amount of power to the flow control valve actuator orto the appropriate sensor through the inductive coupler 74.

Telemetry unit 76, or another suitable independent completion component,may also be used to distribute the power from power unit 44 to all ofthe electrically powered completion components 52. Feedback may becontinuously sent to the surface via the wireless telemetry system 62.The use of power storage device 48 and wireless telemetry system 62enables operation of and control over the independent completion 30 evenduring a well shut-in when no production fluid flows. The localizedpower storage provided by power storage device 48 allows an operator toshut-in the well for a finite period of time while devices 52 arepowered by the power storage device 48. Even during shut-in, sensorreadings regarding pressure build-up and/or other parameters may beobtained and other well testing can be conducted. The resulting data maybe transmitted to the surface with the aid of wireless telemetry system62 during the finite shut-in period.

If a failure event occurs or if an end of service life for power unit 44is anticipated, the entire power unit 44 may be removed by releasing thelocking mechanism 80. The power unit portion of the inductive coupler 74is simply pulled or otherwise disengaged from the remainder of theindependent completion 30 and retrieved to the surface. For example,applying a pulling force to power unit 44 may be used to cause releaseof locking mechanism 80 and disengagement of inductive coupler 74. Asdiscussed above, the entire power unit 44 may be designed with asufficiently small diameter or cross-section so that it may be pulled upthrough an interior of well completion 28. Removal through the interiorof the completion 28 obviates the need to remove any uphole hardware toperform the servicing or replacement operation. After service, the powerunit 44 may simply be re-deployed down through well completion 28 andlocked into place within the independent completion 30 via lockingmechanism 80. As the power unit is moved into position withinindependent completion 30, the inductive coupler also is again connectedto allow for electrical signals to be transmitted from and/or toelectrical devices 52.

However, the components of power unit 44, independent completion 30, andoverall well system 20 can be adjusted to accommodate a variety ofstructural, operational, and/or environmental parameters. For example,various combinations of packers, flow control valves, telemetry systems,power generators, power storage devices, sensors and other componentsmay be used to achieve the desired flow control or other downholefunctional control. Additionally, the number and arrangement of wellboresections and well zones along each wellbore section may varysubstantially from one well application to another. In someapplications, wellbore sections are disposed along lateral wellboreswhile other applications have at least one wellbore section in anon-lateral, e.g. vertical, wellbore. The technique and mechanisms usedto deploy and retrieve the power units also may change from oneapplication to another.

Although only a few embodiments of the present disclosure have beendescribed in detail above, those of ordinary skill in the art willreadily appreciate that many modifications are possible withoutmaterially departing from the teachings of this disclosure. Accordingly,such modifications are intended to be included within the scope of thisdisclosure as defined in the claims.

What is claimed is:
 1. A system for use in a well, comprising: a wellcompletion deployed in a generally vertical wellbore; an independentcompletion deployed in a lateral wellbore, the independent completioncomprising a power unit having a power generator and a power storage tostore energy generated by the power generator, the power unit beingremovably engaged within the independent completion to enable removaland re-engagement of the power unit; and a wireless telemetry systempositioned to communicate signals between the independent completion andthe well completion.
 2. The system is recited in claim 1, wherein theindependent completion further comprises a flow control valve.
 3. Thesystem is recited in claim 1, wherein the independent completion furthercomprises a sensor which receives power from the power storage, whereindata from the sensor is transmitted via the wireless telemetry system.4. The system is recited in claim 1, wherein the independent completionfurther comprises a plurality of electrical devices receiving power fromthe power storage.
 5. The system is recited in claim 1, wherein thepower storage is coupled to an electrical device via an inductivecoupler in the independent completion.
 6. The system as recited in claim1, wherein the power storage comprises a rechargeable battery.
 7. Thesystem as recited in claim 1, wherein the power generator comprises aturbine rotated by fluid flowing along the lateral wellbore.
 8. Thesystem as recited in claim 1, wherein the wireless telemetry systemcomprises an electromagnetic wireless telemetry system.
 9. The system asrecited in claim 1, wherein the wireless telemetry system comprises apressure pulse system.
 10. A method, comprising: placing an independentcompletion in a wellbore section; providing the independent completionwith a removable power unit having a hydraulically driven powergenerator coupled to a power storage; and communicating data between theindependent completion and a second completion located in a secondwellbore section.
 11. The method as recited in claim 10, whereincommunicating comprises communicating data wirelessly.
 12. The method asrecited in claim 10, wherein communicating comprises communicating datato the second completion located in a generally vertical wellboresection.
 13. The method as recited in claim 10, wherein providingcomprises coupling the removable power unit with a remainder of theindependent completion via an inductive coupler and a lock mechanism.14. The method as recited in claim 10, wherein providing comprisesproviding the independent completion with the removable power unithaving the hydraulically driven power generator in the form of a turbineand the power storage in the form of a battery.
 15. The method asrecited in claim 10, further comprising locating the independentcompletion in a lateral wellbore and using a sensor and a flow controlvalve in the independent completion to monitor and control flow in thelateral wellbore, wherein communicating comprises communicating datafrom the sensor to the second completion via wireless telemetry.
 16. Themethod as recited in claim 10, wherein communicating comprisescommunicating via a wireless, acoustic telemetry system.
 17. The methodas recited in claim 10, further comprising removing the removable powerunit through an interior of the second completion.
 18. A system for usein a wellbore, comprising: a remote, independent completion deployed ina wellbore, the remote, independent completion comprising a power unitwhich is selectively engageable and disengageable from a remainder ofthe remote, independent completion, the power unit comprising a powergenerator and a power storage.
 19. The system as recited in claim 18,wherein the remote, independent completion further comprises a wirelesstelemetry system.
 20. The system as recited in claim 19, furthercomprising a second, downhole completion in communication with theremote, independent completion via the wireless telemetry system.